In recent years, organic light-emitting display panels, due to the advantages thereof such as ultra-thinness and lightness, self-illumination, low power consumption, high efficiency, high contrast, and fast response, have become the most popular products in the market following thin film transistor liquid crystal display panels.
FIG. 1 schematically shows one organic light-emitting display panel and pixel units thereof in the prior art. Typically, an organic light-emitting display panel outputs pictures through progressive scanning. That is, scanning signals are transmitted to activate switch transistors (marked as T1 in the figure) in the pixel units line by line, so as to enable drive transistors (marked as T2 in the figure) in the pixel units to receive data voltages characterizing image information. Under co-action of a data voltage and a supply voltage, the drive transistor is activated and generates a corresponding drive current, which is supplied to an organic light-emitting diode (marked as OLED in the figure) and drives the organic light-emitting diode to work. The brightness of the organic light-emitting diode is dependent on a current IOLED flowing therethrough, and the current IOLED equals a drain-source current Ids (also referred to as a drive current) of the drive transistor T2. With regard to the drive transistor T2, the drive current can be determined through the following formula:Ids=K·(Vgs−Vth)2 =K·(OVdd−Vdata−|Vth|)2,wherein K represents an electrical parameter of the drive transistor, and Vgs, Vth, OVdd, and Vdata respectively indicate gate-source voltage of the drive transistor, threshold voltage of the drive transistor, supply voltage, and data voltage.
It is indicated in the above formula, the drive current is closely related to the supply voltage, the data voltage, and the electrical parameter (such as channel dimension and threshold voltage) of the drive transistor.
Theoretically, all the pixel units located on one and a same display panel will use one type of drive transistors, and operate under a same voltage source. Therefore, when the pixel units are each input with a same data voltage, all the pixel units will have the same drive current flowing through respective organic light-emitting diodes, thereby enabling identity in time and homogeneity in space with respect to brightness of the organic light-emitting diodes in all the pixel units. However, this is not actually the case. Influenced by various factors such as technological conditions, particularly voltage division by resistance of a power wiring per se, drive currents flowing through the light-emitting diodes of all the pixel units will be different from one another, thereby causing brightness distortion and inhomogeneous brightness of the pixel units on the display panel. In particular, as the display technology develops in recent years, display panels are increasingly larger-sized. Accordingly, the power wiring supplying power to the pixel units is becoming longer. This deteriorates the problem of inhomogeneous brightness of the display panel, and becomes an urgent problem to be solved in the field.